gistfile1.txt

in my controller:
--------------------

$form = SalesForm::create($this->get('form.context'), 'sale', array('em' => $em));

in my SalesForm:
--------------------

class SalesForm extends Form
{
    protected function configure()
    {
    	$this->addRequiredOption('em');
    	
        $this->add(new TextField('city', array(
        	'required' => true,
            'max_length' => 100,
        )));
        
        $this->add(new TextField('sale', array(
        	'required' => true,
        )));
        
        $this->add(new EntityChoiceField('rep_id', array(
        	'em' => em,
        	'class' => 'Aware\\SalesBundle\\Entity\\Rep',
        	'property' => 'name',
        	'query_builder' => function($repository) { 
            	return $repository->createQueryBuilder('rep');
        	}
        )));
    }
}